Reversing unit for a hand-held power tool

ABSTRACT

A reversing unit for a hand-held power tool has a reversing device for reversing an output direction, a drive unit, a tool unit drivable in rotary manner through at least one semi-revolution by the drive unit, and a protection unit provided for at least partially compensating for driving of the tool unit in one output direction in at least partially automated manner by a compensating device in a reverse direction.

CROSS-REFERENCE TO A RELATED APPLIACTION

The invention described and claimed hereinbelow is also described in German Patent Application DE 102005057268.5 filed on Dec. 1, 2005. This German Patent Application, whose subject matter is incorporated here by reference, provides the basis for a claim of priority of invention under 35 U.S.C. 119(a)-(d).

BACKGROUND OF THE INVENTION

The present invention relates to reversing units for a hand-held power tool with a reversing device.

Hand-held power tools are known, in particular drills which have an additional screwing function. In the case of these hand-held power tools, a tool can be driven in a rotary manner in two different output directions. In order to reverse the output direction, the hand-held power tool is provided with a mechanical reversing device which includes an actuating device. After an operator has reversed the output direction, driving of the tool in the reverse output direction can be started by further actuation of a driving switch.

SUMMARY OF THE INVENTION

The invention is based on a reversing unit for a hand-held power tool, with a reversing device for reversing an output direction, in which a tool unit can be driven in a rotary manner through at least one semi-revolution by a drive unit.

It is proposed that the reversing unit for a hand-held power tool has a protection unit which is provided for the purpose of at least partially compensating for driving the tool unit in one output direction in an at least partially automated manner by means of a compensating drive in the reverse direction. This makes it possible to achieve a high level of safety during operation of a hand-held power tool, in particular a drill. The compensating drive makes it possible to oppose, in particular hair, body parts and/or items of clothing being strongly pulled into the rotating tool unit, which may lead to an operator suffering severe injuries. In this connection, a “tool unit” is to be understood as meaning, in particular, an element or a unit of elements of the hand-held power tool which are connected in a rotationally fixed manner to an output shaft of the hand-held power tool, such as, for example, a tool, a tool holding fixture, an additional unit for inserting into the tool holding fixture, etc.

The protection unit is advantageously provided for the purpose of automatically switching on the compensating drive as a function of a retention signal which signals that driving is being maintained in one output direction. As a result, if, during the driving of the tool unit, the operator perceives that there is the risk of, for example, hair, items of clothing and/or body parts being pulled in, rapid activation of the compensating drive can be achieved. Protection modes for the hand-held power tool are conceivable, in which the retention signal is generated, for example, by actuation of an emergency switching-off element or by letting go of a driving switch.

In a further embodiment of the invention, it is proposed that the protection unit is provided for the purpose of automatically switching on the compensating drive in the reverse direction after a preset rotational travel of the tool unit in one output direction is completed. This makes it possible to achieve a high level of safety during operation of the hand-held power tool, said level of safety being suitable, in particular, for DIY by children. For example, a child protection mode can be obtained, in which a small rotational travel of the tool unit is set prior to operation, and the compensating drive is switched on automatically, without involvement of the child, after this rotational travel is completed. The rotational travel can be designed as an angle of rotation or as a number of revolutions of the tool unit.

In addition, it is proposed that the protection unit is provided for the purpose of at least substantially compensating for a rotational travel of the tool unit completed during driving by means of a compensating drive. This is advantageously suitable for uses of the hand-held power tool in which the latter is operated with small rotational travels of the tool unit, such as, in particular, during DIY by children. The rotational travel is preferably substantially compensated for if, after completion of the rotational travel, the tool unit is driven in the reverse direction by at least 70% and preferably more than 80%, in particular more than 90%, of the rotational travel.

In a further embodiment of the invention, it is proposed that the reversing unit for the hand-held power tool includes a setting unit which is provided for setting a rotational travel of the tool unit. This makes it possible to achieve a high level of operating convenience of the hand-held power tool. With the setting unit, a maximum rotational travel for driving in the output direction and/or for the compensating drive in the reverse direction can be set.

It is furthermore proposed that the reversing unit for a hand-held power tool includes a setting unit which is provided for the purpose of setting a protection mode, thus enabling a high level of flexibility to be achieved in the use of the hand-held power tool.

A further embodiment makes provision for the reversing device to be provided for reversing the output direction during running of the drive unit. A delay in the reversing of the output direction that can be attributed to inertia of driving elements during holding and starting of the drive unit can thereby be advantageously reduced.

In this connection, it is proposed that the reversing device comprises a coupling device, thus making it possible for existing and cost-effective elements to be used for the reversing device.

The coupling device preferably has at least two coupling elements which are provided relative to each other for opposed rotation during running of the drive unit. This makes it possible to achieve a particularly simple construction of the coupling device. For example, an output element connected in a rotationally fixed manner to the tool unit can be arranged displaceably between the coupling elements. During a reversing operation, said output element can be coupled to one of the coupling elements depending on the desired output direction.

If the protection unit can be switched on and off, an advantageous level of flexibility can be achieved in the use of the hand-held power tool.

Further advantages emerge from the description below of the drawing. The drawing illustrates an exemplary embodiment of the invention. The drawing, the description and the claims contain numerous features in combination. A person skilled in the art will expediently also consider the features individually and put them together to form meaningful further combinations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a drill with internal elements in a side view in accordance with the present invention,

FIG. 2 shows a setting unit of the drill from FIG. 1 in accordance with the present invention, and

FIG. 3 shows a coupling device of the drill from FIG. 1 in accordance with the present invention.

DESCRIPTION FO THE PREFERRED EMBODIMENTS

FIG. 1 shows a hand-held power tool 10 designed as a drill. It has a housing 12 with a handle 14 and a drive switch 16. A tool holding fixture 18 and a tool 20 fastened in the tool holding fixture 18 can also be seen. The tool holding fixture 18 and the tool 20 form a tool unit 22. The tool 20 is designed as a drill bit in the figure. The tool unit 22 is connected to an output shaft 24 in a rotationally fixed manner. The latter is coupled via a gear unit 26 to a drive unit 28 which comprises an electric motor 30 and a drive shaft 32. The tool unit 22 can be driven by the drive unit 28 via the output shaft 24 in a rotary manner through at least one semi-revolution in one output direction 34 (right-handed rotation) and in an output direction 36 (left-handed rotation) opposed to the output direction 34. During use of the hand-held power tool 10 as a drill, the tool unit 22 is driven in the output direction 34.

The hand-held power tool 10 is furthermore provided with a reversing unit 37. The latter has a reversing device 38 which is arranged in the gear unit 26 and serves to reverse the output direction 34 or 36 during operation of the hand-held power tool 10. The construction and the operation of the reversing device 38 are described in more detail with reference to FIG. 3. In addition, the reversing unit 37 for a hand-held power tool comprises a protection unit 40 which is provided for the purpose of at least partially compensating for driving the tool unit 22 in the output direction 34 or 36 in an at least partially automated manner by means of a compensating drive in the reverse output direction 36 or 34. For this purpose, the protection unit 40 is provided with an electronic control unit 42 which is connected electrically to the electric motor 30, the reversing device 38 and a sensor unit 44 assigned to the drive switch 16. Furthermore, the control unit 42 is connected to a setting unit 46 which is integrated in the handle 14.

The control unit 42 can be programmed by an operator via the setting unit 46, which is illustrated in a front view in FIG. 2. Said control unit has actuating elements 48 and an LED indicating device 50. The setting unit 46 enables the operator to switch the protection unit 40 on and off. When the protection unit 40 is switched off, the control unit 42 does not have any influence on the drive unit 28 and the reversing device 38, with it being possible for the hand-held power tool 10 to be operated as a conventional drill or powered screwdriver. When the protection unit 40 is switched on, the operator can select a certain protection mode of the protection unit 40 by means of the actuating elements 48 and the LED indicating device 50.

It is assumed first of all that the hand-held power tool 10 is used for DIY, for example drilling of a workpiece, by a child. The operator can set a child protection mode by means of the setting unit 46. During operation in this child protection mode, which corresponds to a high level of safety, when the drive switch 16 is actuated, the tool unit 22 is driven through a predetermined, limited number of revolutions in the output direction 34. This number can likewise be input by the operator via the actuating elements 48. After the predetermined rotational travel of the tool unit 22 in the output direction 34 is completed, the control unit 42 automatically switches on a compensating drive of the tool unit 22.

For this purpose, the control unit 42 controls the reversing device 38 and the drive unit 28. During this compensating drive, the tool unit 22 is driven by the same predetermined number of revolutions in the output direction 36. After the compensating drive has finished, the control unit 42 again switches on driving in the output direction 34 with the predetermined number of revolutions, which, after completion, is compensated for again by a compensating drive in the output direction 36, etc. This cycle of drive and compensating drive is repeated until the child lets go of the drive switch 16. In this child protection mode, by limiting the revolutions—advantageously to a small number—and by the fully automatic switching on of the compensating drive by the control unit 42, the risk of body parts and/or items of clothing being strongly pulled in can be reduced.

It is furthermore conceivable that switching from this child protection mode into a further mode takes place by means of an access authorization, for example by a code being input by means of the setting unit 46. This makes it possible to avoid a child switching off the child protection mode selected specifically for his DIY and using the hand-held power tool 10 in a mode with a lower safety level.

It is now assumed that the hand-held power tool 10 is being used by an adult. By means of the setting unit 46, the operator can select a corresponding protection mode which corresponds to a medium level of safety. In this protection mode, the tool unit 22 can be driven in the output direction 34 without limiting the number of revolutions. After maintaining this drive, a compensating drive of the tool unit 22 in the output direction 36 is started. This is realized by means of the sensor unit 44, which is connected to the drive switch 16, and the control unit 42. If the operator lets go of the drive switch 16 during driving, for example in a hazardous situation, the sensor unit 44 sends a retention signal to the control unit 42. The latter subsequently controls the reversing device 38 and the drive unit 28, so that the compensating drive is switched on. During this compensating drive, the tool unit 22 is driven through a predetermined number of revolutions in the output direction 36. This number can likewise be predetermined by the operator by means of the setting unit 46.

Furthermore, the protection unit 40 is provided with a further protection mode which corresponds to a low level of safety. In this protection mode, a retention signal can be transmitted to the control unit 42 and the compensating drive will therefore be started by the operator actuating an emergency trip switch 52. The hand-held power tool 10 can be used as a conventional hand-held power tool by the operator until the emergency trip switch 52 is actuated.

The construction and the operation of the reversing device 38 are explained with reference to FIG. 3. The reversing device 38 is provided for the purpose of reversing an output direction of the tool unit 22 during running of the drive unit 28. For this purpose, the reversing device 38 comprises a coupling device 54 with a first coupling element 56, which is designed as a coupling disk and can be driven to rotate in the output direction 34 or 36 by the drive unit 28, and with a second coupling element 58, which is designed as a coupling disk and can be driven to simultaneously rotate in the output direction 36 or 34 by the drive unit 28. In addition, the coupling device 54 has a carry-along element 60 which is connected to the output shaft 24 in a rotationally fixed manner. Said carry-along element is arranged between the coupling elements 56, 58 in a manner such that it can be displaced in the axial direction 61 and can be adjusted until it comes into contact with the first or the second coupling element 56, 58.

For this purpose, the carry-along element 60 is movable on the output shaft 24 in a translatory manner in the axial direction 61. The first coupling element 56 can be driven by the drive shaft 32 of the drive unit 28 via a gear 62 to rotate in the output direction 34 or 36. The second coupling element 58 can be driven via an intermediate shaft 64 with teeth to rotate in the output direction 36 or 34. The carry-along element 60 is led through the first coupling element 56. To drive a translatory movement of the carry-along element 60, the reversing device 38 is provided with an adjusting unit 66 which is controlled by the control unit 42 during a reversal of the output direction. For this purpose, the adjusting unit 66 is connected to the control unit 42 via an electric connection 68.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the type described above.

While the invention has been illustrated and described as embodied in a reversing unit for a hand held power tool, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, be applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims. 

1. A reversing unit for a hand-held power tool, comprising a reversing device for reversing an output direction; a drive unit; a tool unit drivable in rotary manner through at least one semi-revolution by said drive unit; a protection unit provided for at least partial compensating for driving of said tool unit in one output direction in at least partially automated manner by a compensating drive in a reverse direction.
 2. A reversing unit as defined in claim 1, wherein said protection unit is configured for automatically switching on said compensating drive as a function of a retension signal which signals that driving is being maintained in the one output direction.
 3. A reversing unit as defined in claim 1, wherein said protection unit is configured for automatically switching on said compensating drive in the reverse direction after a preset rotational travel of said tool unit in the one output direction is completed.
 4. A reversing unit as defined in claim 1, wherein said protection unit is configured for at least substantially compensating for a rotational travel of said tool unit completed during driving by said compensating drive.
 5. A reversing unit as defined in claim 1; and further comprising a setting unit configured for setting a rotational travel of said tool unit.
 6. A reversing unit as defined in claim 1; and further comprising a setting unit configured for setting a protection mode.
 7. A reversing unit as defined in claim 1, wherein said reversing device is configured for reversing the output direction during running of said drive unit.
 8. A reversing unit as defined in claim 1, wherein said reversing device comprises a coupling device.
 9. A reversing unit as defined in claim 8, wherein said coupling device has at least two coupling elements which are provided for opposite rotation relative to each other during running of said drive unit.
 10. A reversing unit as defined in claim 1, wherein said protection unit is configured so that it is switchable on and off.
 11. A hand-held power tool, comprising a reversing unit, said reversing unit including a reversing device for reversing an output direction, a drive unit, a tool unit drivable in rotary manner through at least one semi-revolution by said drive unit, a protection unit provided for at least partially compensating for driving of said tool unit in one output direction in at least partially automated manner by a compensating drive in a reverse direction. 